Roadside Associated Disturbance on Coastal Dunes

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by R. I. Lonard, Univ of Texas-Pan American, Edinburg, United States,
F. W. Judd, Univ of Texas-Pan American, Edinburg, United States,
J. H. Everitt, Univ of Texas-Pan American, Edinburg, United States,
D. E. Escobar, Univ of Texas-Pan American, Edinburg, United States,
R. Davis, Univ of Texas-Pan American, Edinburg, United States,

Document Type: Proceeding Paper

Part of: Coastal Zone '91

Abstract: Park Road 100 extends through the developed southernmost 8 km of South Padre Island and continues northward for 11.5 km through the Secondary Dunes and Vegetated Flats (SDVF) zone of the island. Pushing sand from the road onto adjacent vegetation, vehicular traffic, and camping adjacent to the road kills vegetation and exacerbates the movement of sand by winds. Windblown sand covers and kills vegetation creating more and larger bare areas. In December 1985 we established transects at 15 sites along Park Road 100 to assess the magnitude of disturbance to vegetation and to investigate the pathway of recovery. The transects were censused 25 times between December 1985 and December 1988. Hurricane Gilbert made landfall in northeastern Mexico on 16 September 1988 causing major damage to Park Road 100 and significant changes to the adjacent vegetation. We compared assessments of vegetative cover made from a SPOT satellite image obtained 3 November 1988 with a color infrared (CIR) aerial photograph obtained 4 November 1988 to evaluate the impact of the hurricane and to establish a baseline for future comparisons of vegetative cover. The Percent of cover was significantly lower on east transects where natural disturbance was greater. There was no significant variation in percent cover among seasons and species richness did not vary significantly among seasons or between locations. Which species colonized first (as well as second or third) was stochastic. Percent cover and species richness were significantly lower on the west transects after Hurricane Gilbert. Computer classification of island-wide vegetative cover after Hurricane Gilbert was 6.5% for a CIR aerial photograph and 5.0% for a SPOT satellite image.

Subject Headings: Highways and roads | Vegetation | Dunes | Hurricanes and typhoons | Aerial photography | Islands | Parks | Sandy soils | North America | Mexico | Texas | United States

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